In known gear pumps of this type, the bearings are lubricated by the product being conveyed. In many applications of such gear pumps, the demand is being made today that the pump should be cleanable on-site, that is, in the installed state, by the use of a flushing agent, which is transported by the pump just like the product conveyed by the gear pump. Experience has shown, however, that deposits formed by the conveyed product often remain behind in the pump. In cases of strict requirements on the purity of the product, this type of cleaning is thus not sufficiently effective, because fresh product can become contaminated by these deposits.
Depending on the flow behavior, another problem with the products conveyed by known gear pumps is that the residence times are often widely distributed. In the case of sensitive products, such residence time distributions can frequently make it necessary to shut down operation to allow the equipment to be cleaned.